Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$46.77	13.343%	$53.0105	$53.01	$53.00	$53.00
Purchase #2	$184.68	6.755%	$197.1551	$197.16	$197.15	$197.20
Purchase #3	$242.56	13.409%	$275.0849	$275.08	$275.10	$275.10
Purchase #4	$114.88	10.553%	$127.0033	$127.00	$127.00	$127.00
Purchase #5	$67.61	13.789%	$76.9327	$76.93	$76.95	$76.90
Purchase #6	$122.82	3.713%	$127.3803	$127.38	$127.40	$127.40
Purchase #7	$34.82	10.763%	$38.5677	$38.57	$38.55	$38.60
7 purchase totals =	$814.14		$895.1345	$895.13	$895.15	$895.20